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Assignment statements in Python do not copy objects, they create bindings
between a target and an object. For collections that are mutable or contain
mutable items, a copy is sometimes needed so one can change one copy without
changing the other. This module provides generic shallow and deep copy
operations (explained below).

keeping a “memo” dictionary of objects already copied during the current
copying pass; and

letting user-defined classes override the copying operation or the set of
components copied.

This module does not copy types like module, method, stack trace, stack frame,
file, socket, window, array, or any similar types. It does “copy” functions and
classes (shallow and deeply), by returning the original object unchanged; this
is compatible with the way these are treated by the pickle module.

Shallow copies of dictionaries can be made using dict.copy(), and
of lists by assigning a slice of the entire list, for example,
copied_list=original_list[:].

Changed in version 2.5: Added copying functions.

Classes can use the same interfaces to control copying that they use to control
pickling. See the description of module pickle for information on these
methods. The copy module does not use the copy_reg registration
module.

In order for a class to define its own copy implementation, it can define
special methods __copy__() and __deepcopy__(). The former is called
to implement the shallow copy operation; no additional arguments are passed.
The latter is called to implement the deep copy operation; it is passed one
argument, the memo dictionary. If the __deepcopy__() implementation needs
to make a deep copy of a component, it should call the deepcopy() function
with the component as first argument and the memo dictionary as second argument.